The present invention relates to measuring vehicle tire air pressure and utilizing these measurements.
The air pressure within inflated vehicle tires is an important parameter for vehicle operation. Vehicle dynamics are closely linked to tire performance. These dynamics affect many aspects of vehicle operation, including handling, braking, rollover characteristics, and the like. Tire pressure also affects the life of the tire. Excess tire pressure may make the tire more susceptible to puncture and, if extreme, to burst damage. Tire under-pressure may result in the generation of excess heat, particularly at elevated vehicle speeds. To ensure proper tire performance, vehicle tires are typically given a range of inflation pressures based on the tire type, vehicle type, vehicle configuration and use, expected driving conditions, and the like. Despite its importance, tire inflation pressure may at times fall outside of specified ranges. Tires often lose air pressure gradually, making the point at which inflation pressure drops below the specified value difficult to detect. Many air pressure gauges for use with vehicle tires are inaccurate, resulting in under-inflation or over-inflation even when proper care is taken. Further, modern run-flat tires provide limited performance even in the presence of substantial pressure loss, making such loss difficult for the vehicle operator to detect.
In-vehicle tire pressure monitoring systems are currently available. Typically, these systems include a tire pressure sensor built into the tire or attached to the tire valve stem. Each sensor relays measured tire pressure to an associated receiver via a wireless link. Tire pressure information is then provided to the vehicle operator by an indicator or graphic display on the vehicle dashboard. Such a display, however, may not solve the problem of out-of-range tire pressure if the display is either unnoticed, misinterpreted, or ignored by the vehicle operator. What is needed is to automatically reduce the effects of out-of-range vehicle tire pressure.
The present invention automatically controls vehicle speed if the vehicle speed is not appropriate for measured tire air pressure, measure tire temperature, or both.
A method of limiting vehicle speed is provided. The air pressure and temperature in at least one tire are sensed, as well as the vehicle speed. At least one threshold is determined based on at least one parameter of vehicle operation. A determination is made as to whether or not the vehicle speed is appropriate for each tire based on the sensed tire air pressure, the sensed tire temperature and on each determined threshold. The vehicle speed is automatically controlling if the vehicle speed is not appropriate for each tire.
In various embodiments of the present invention, the vehicle speed is determined to be not appropriate for the tire if the tire pressure is greater than a maximum pressure threshold, if the tire pressure is less than a minimum threshold, if the tire temperature is greater than a maximum temperature threshold and/or if the tire temperature is less than a minimum temperature threshold.
In other embodiments of the present invention, the at least one parameter of vehicle operation consists of at least one from a set including vehicle speed, vehicle load, vehicle load distribution, four-wheel drive mode, towing mode, automatic suspension mode, traction control operation, automatic brake system control, tire location, tire air pressure, air pressure in other tires, tire temperature, temperature in other tires, ambient air pressure, and ambient temperature.
A system for limiting vehicle speed is also provided. The system includes at least one tire pressure sensor generating a pressure signal based on the pressure of air within a tire. At least one tire temperature sensor generates a temperature signal based on the temperature within the tire. A vehicle speed sensor generates a signal based on vehicle speed. A power plant causes the vehicle to move at the vehicle speed based on power plant control signals. Control logic generates at least one power plant control signal to automatically control vehicle speed if the vehicle speed is not appropriate for at least one tire based on the sensed tire air pressure, sensed tire temperature and on at least one vehicle operating condition.
A method of limiting vehicle speed is also provided. Tire pressure in at least one tire is determined based on pressure sensed within the tire. The vehicle speed is determined. The vehicle maximum speed is automatically limited if the vehicle speed is not appropriate for each tire based on the sensed tire air pressure. Tire temperature is determined in the at least one tire based on temperature sensed within the tire. Vehicle maximum speed is automatically limited if the vehicle speed is not appropriate for each tire based on the sensed tire temperature. Vehicle speed is also automatically limited if the vehicle speed is not appropriate for each tire based on the sensed tire temperature and based on the sensed tire pressure.
These and other objects, features and advantages of the invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in conjunction with the accompanying drawings.